Valve structure for a compressor

ABSTRACT

A variable displacement compressor includes a rotary valve coupled to a drive shaft. The rotary valve is centrally received in a suction chamber of the variable displacement compressor and extends through an aperture formed in a cylinder block thereof. The rotary valve has a suction opening cooperating with the cylinders to successively provide a direct fluid communication between the suction chamber and each of the cylinders.

FIELD OF THE INVENTION

The present invention relates to a variable displacement compressor for use in an air conditioning system for a vehicle, and more particularly to a rotary valve structure of a variable displacement compressor for supplying a refrigerant gas into a cylinder to be compressed.

BACKGROUND OF THE INVENTION

As commonly known, variable displacement compressors having a swash plate are used in air conditioning systems of motor vehicles. Such compressors typically include at least one piston disposed in a cylinder of a cylinder block and a rotor assembly operatively coupled to a drive shaft. The swash plate is coupled to and caused to rotate by the rotor assembly. The swash plate is variably angled relative to the rotor between a minimum angle and a maximum angle. Each piston slidably engages with the swash plate through a shoe as the swash plate rotates causing the piston to reciprocate within the cylinder. As the angle of the swash plate relative to the rotor varies, the stroke of each piston is varied and, therefore, the total displacement or capacity of the compressor is varied.

In variable displacement compressors having a swash plate, reciprocation of the pistons within the cylinders results in each of the pistons executing a suction stroke or a compression stroke. During the suction stroke, a refrigerant gas is delivered from a suction chamber of the compressor to the cylinder through a suction port. During the compression stroke, the refrigerant gas is compressed and delivered into a discharge chamber of the compressor through a discharge port. The compressor typically includes a suction reed valve and a discharge reed valve, wherein during the suction stroke the suction reed valve is open and the discharge reed valve is closed and during the compression stroke the suction reed valve is closed and the discharge reed valve is open.

However, certain disadvantages are encountered with the use of reed valves. For example, the reed valves are typically in a normally closed configuration and require a sufficient pressure differential to overcome a spring force thereof to effectively open. Specifically, the suction reed cannot open properly unless a pressure difference between the cylinder and the suction chamber is sufficient to overcome the spring force thereof. Moreover, oil in the compressor can cause the reed valves to stick. As a result, an opening of the reed valve is delayed, an efficiency of the compressor is minimized, and pressure pulsations which result in an undesirable noise vibration harshness (NVH) are maximized. Additionally, due to a geometry and a maximum bending stress of the reed valves, the flow area of the refrigerant gas through the suction port and discharge port is limited. Furthermore, because the reed valves often do not open or close properly due to at least the above reasons, the reed valves begin to “float.” Floating causes improper sealing and internal leakage.

To overcome some of these deficiencies, a rotary valve has been included in variable displacement compressors to replace the reed valves. For example, in U.S. Pat. No. 6,675,607 to Tarutani et al., a variable displacement compressor with a swash plate using a rotary valve for supplying a refrigerant gas into a gas compression chamber is disclosed. The rotary valve is formed at a rear end portion of a shaft and integrally formed with the shaft. The rotary valve integrally rotates with the shaft as the shaft is rotated. A suction port communicating with a bleeding channel of the shaft is formed in the rotary valve. Suction channels of cylinder bores communicate with the suction port in succession according to the rotation of the shaft and the rotary valve. The suction channels are formed inside the cylinder block and communicate with the cylinder bores via a side wall forming the cylinder bore.

Additionally, in U.S. Pat. No. 5,562,425 to Kimura et al., a rotary valve for use in piston type compressor is disclosed. The rotary valve is retained in a valve chamber formed in a central portion of a rear housing. The valve chamber communicates with a suction chamber. The rotary valve includes a slot formed in a central portion of the rotary valve in which a drive shaft engages with to transmit rotation to the rotary valve. A suction passage having an inlet and outlet is formed in the rotary valve.

However, these valve structures do not provide a maximum suction flow of the refrigerant gas and/or provide an increase in a dead volume ratio when the compressor is in a variable displacement mode. Additional disadvantages include poor sealing of and undesired leakage of the refrigerant gas to undesired areas of the compressor. Furthermore, the rotary valve structures do not provide desired thermal properties, durability, balance, and bearing properties to minimize deflections thereof and operatively maintain desired efficiency of the compressor.

Therefore, there is a continuing need for a rotary valve structure that maintains a maximum suction flow of refrigerant gas while minimizing a dead volume ratio of the compressor. Additionally, there is a continuing need for a rotary valve structure having desired thermal properties, durability, balance, sealing properties and features, to operatively maintain a desired efficiency of the compressor.

SUMMARY OF THE INVENTION

Concordant and congruous with the present invention, a rotary valve structure that maintains a maximum suction flow of refrigerant gas while minimizing a dead volume ratio of the compressor, while also having desired thermal properties, durability, balance, sealing properties and features, to operatively maintain a desired efficiency of the compressor has surprisingly been discovered.

According to an embodiment of the invention, a rotary valve for controlling a supply of refrigerant gas to cylinders in a variable displacement compressor is disclosed. The rotary valve includes a disc portion and a substantially cylindrical stem portion extending axially from the disc portion. The disc portion and the stem portion are configured to be coupled to a drive shaft of the compressor. A suction opening formed in the disc portion and configured to permit direct fluid communication between a suction chamber and at least one cylinder of the compressor.

According to another embodiment of the invention, a rotary valve assembly for controlling a supply of refrigerant gas to cylinders in a variable displacement compressor is disclosed. The rotary valve assembly includes a rotary valve including a disc portion and a substantially cylindrical stem portion extending axially from the disc portion. The disc portion and the stem portion are configured to be coupled to a drive shaft of the compressor. A suction opening is formed in the disc portion. A valve plate assembly includes a central aperture formed therein. The aperture receives the rotary valve. A plurality of suction apertures are formed in the valve plate assembly, wherein the suction opening aligns with at least one of the suction apertures to permit direct fluid communication between a suction chamber and at least one cylinder of the compressor.

According to a further embodiment of the invention, a variable displacement compressor is disclosed. A cylinder block has a plurality of cylinders annularly formed therein and a centrally formed aperture. A plurality of pistons are received within the cylinders. A rear head is disposed adjacent one end of the cylinder block and defining a suction chamber and discharge chamber. A crank case forming a crank chamber is adjacent an other end of the cylinder block. A drive shaft is rotatably received in the aperture of the cylinder block and extends through the crank chamber. A swash plate assembly is coupled to the drive shaft, the swash plate assembly is operably coupled to the pistons to cause a reciprocating motion thereof. A rotary valve is coupled to the drive shaft. The rotary valve is centrally received in the suction chamber and extends through the aperture formed in the cylinder block, wherein the rotary valve has a suction opening cooperating with the cylinders to successively provide a direct fluid communication between the suction chamber and each of the cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:

FIG. 1 is a cross-sectional elevational view of a variable displacement compressor according to an embodiment of the invention;

FIG. 2 is a front elevational view of a rotary valve of the variable displacement compressor of FIG. 1;

FIG. 3 is a left side elevational view of the rotary valve of FIG. 2;

FIG. 4 is a right side perspective view of the rotary valve of FIGS. 2 and 3;

FIG. 5 is an enlarged fragmentary cross-sectional elevational view of the variable displacement compressor highlighted by circle 5 in FIG. 1, showing a valve plate assembly according to an embodiment of the invention;

FIG. 6 is a left side perspective view of a valve plate and a wear plate of the valve plate assembly of FIG. 5; and

FIGS. 7A-7D are a left side schematic diagram of the rotary valve at varying rotational positions with respect of a valve plate assembly and a cylinder block.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.

FIG. 1 illustrates a variable displacement compressor 10 according to an embodiment of the invention. The compressor 10 includes a cylinder block 12 having a plurality of cylinders 14 annularly formed therein and reciprocatingly receiving a plurality of pistons 16. Bearing shoes 17 operatively engage the pistons 16 with a swash plate assembly 18 disposed at an inclination angle. The swash plate assembly 18 is rotatingly coupled to a rotor assembly 20 to convert rotary movement of the rotor assembly 20 to reciprocating movement of the pistons 16 within the cylinders 14. The rotor assembly 20 is rotatingly coupled to a drive shaft 24. A hinge mechanism 26 couples the swash plate assembly 18 to the rotor assembly 20 to cause the swash plate assembly 18 to rotate with the drive shaft 24 and variably change inclination angles with respect to the rotor assembly 20.

A rear head 28 is disposed adjacent one end of the cylinder block 12 and sealingly closes the end of the cylinder block 12. A valve plate assembly 30 is disposed between the cylinder block 12 and the rear head 28. The rear head 28 includes a suction chamber 32 for receiving a refrigerant gas and a discharge chamber 34 for receiving a compression gas. The suction chamber 32 communicates with the cylinders 14 through suction apertures 36 formed in the valve plate assembly 30, wherein each of the suction apertures 36 is are aligned with one of the cylinders 14. The cylinders 14 communicate with the discharge chamber 34 through a discharge port 38 disposed in the valve plate assembly 30. A crank case 40 is sealingly disposed adjacent an opposing end of the cylinder block 12. The crank case 40 and the cylinder block 12 cooperate to form an airtight crank chamber 42.

The drive shaft 24 is centrally disposed in and extends through the crank case 40 and the cylinder block 12. The drive shaft 24 is rotateably and linearly supported by bearings mounted in the crank case 40 and the cylinder block 12. The rotor assembly 20 and the swash plate assembly 18 are disposed within the crank chamber 42. The swash plate assembly 18 is slideably and swingably supported by the drive shaft 24 extending through an aperture 56 formed in the swash plate assembly 18. A spring 58 surrounds an outer surface of the drive shaft 24 and is interposed between the rotor assembly 20 and the swash plate assembly 18.

A rotary valve 62 is centrally received in the suction chamber 32 and extends through an aperture 64 formed in a center portion of the cylinder block 12. A first end 23 of the drive shaft 24 partially extends into the suction chamber 32. The rotary valve 62 is coupled to rotate with and radially aligned with the first end 23 of the drive shaft 24 and is adapted to selectively seal each of suction apertures 36 aligned with each of the cylinders 14 during a rotation of the rotary valve 62. The rotary valve 62 is axially secured to the drive shaft 24 by a retaining feature 66. In certain embodiments, as illustrated in the embodiment shown in FIG. 1, the retaining feature 66 shown is a retaining nut and bearings. However, it is understood that the retaining feature 66 can be any feature configured to axially secure the rotary valve 62 to the drive shaft 24 such as a retaining pin, latch, clamp or any other retaining feature, as desired. The rotary valve 62 is radially aligned with the drive shaft 24 with a locating feature (not shown) disposed on or integrally formed with the drive shaft 24. In a non-limiting example, the locating feature can be a key or spline, for example. However, it is understood, the locating feature can be any locating feature such as locating pins or cams or any other locating feature as desired.

FIGS. 2-4 show the rotary valve 62. The rotary valve 62 is substantially mushroom shaped and includes a disc portion 70 integrally formed with a stem portion 72. The disc portion 70 has a first surface 74, a second surface 76, and an outer circumferential wall 84. The disc portion radially extends between walls 60 of the rear head 28 forming the suction chamber 34. An aperture 80 is centrally formed in the rotary valve 62 and is configured to receive the drive shaft 24. A locating slot 82 continuous with the aperture 80 is formed in the rotary valve 62 and configured to engage with the locating feature of the drive shaft 24. In certain embodiments, the rotary valve 62 includes a balancing feature 88, such as a protrusion 89 and a recess 90 formed on the first surface 74 of the disc portion 70. The protrusion 89 is configured as a counterweight. Each of the protrusion 89 and the recess 90 is configured to balance the rotary valve 62 against a suction force as the rotary valve 62 rotates and militate against deflections thereof. The balancing feature can be any balancing feature as desired such as any surface feature, weight, or any other force generating mechanical device to balance the rotary valve 62, for example. The rotary valve 62 can be formed from durable material such as aluminum, aluminum alloy, or steel, for example. Although, other materials or coatings or combinations of materials and coatings can be used as desired such as steel, polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), electroless nickel alloys, or any other metal or material as desired.

The disc portion 70 further includes a suction opening 86 configured to align with the suction apertures 36 formed in the valve plate assembly 30 and the corresponding cylinders 14. The suction opening 86 extends arcuately in respect of a center of the disc portion 70 and is disposed at a radial distance from the center of the rotary valve 62 to axially align a flow of refrigerant from the suction chamber 32 to each cylinder 14. The suction opening 86 illustrated is a continuous arcuate shaped opening. However, the suction opening 86 can be a series of separate suction openings. The suction opening 86 can also be any shape such as circular, rectangular, ovular, or any other shape as desired to align with the suction apertures 36 and corresponding ones of the cylinders 14. The suction opening 86 extends arcuately at an angle α so that the suction opening 86 axially aligns with at least two suction apertures 36 and corresponding ones of the cylinders 14 at any given position of rotation. For example, the suction opening 86 can be adapted to extend at the angle α to axially align with four suction apertures 36 and corresponding ones of the cylinders 14. In certain embodiments, the angle α can be between about 90 degrees and 180 degrees such as 148 degrees, for example. Although the angle α can be any angle less than 90 degrees or greater than 180 degrees as desired.

The stem portion 72 is substantially cylindrical to facilitate coupling to the drive shaft 24 and extends through an aperture formed in the cylinder block 12. A collar 78 is formed adjacent the second surface 76 of the disc portion 70 in the stem portion 72. The collar 78 is an inwardly projecting recess that cooperates with the cylinder block 12 to facilitate smooth rotation of the rotary valve 62. In certain embodiments, the stem portion 72 can be coated or sprayed with a low friction or seizure resistant material to facilitate bearing characteristics so that the stem portion 72 can be configured as a shaft bearing interfacing with the cylinder block 12. The low friction or seizure resistant material can be PTFE, Ni-PTFE, or any other low friction material or coating as desired.

The rotary valve 62 further includes a distribution feature 92 configured to generate a film of lubricant thereon. The lubricant is a volume of oil contained in the crank case 40 that flows from the crank case 40 to the suction chamber 32. The distribution feature shown includes a plurality of grooves 94 formed on the outer wall 84 of the disc portion 70 of the rotary valve 62 and a channel 98 formed on the second surface 76 of the disc portion 70 of the rotary valve 62. The grooves 94 are in fluid communication with the channel 98 via a radially formed passage 100 extending from the outer wall 84 to an opening 102 formed on the second surface 76 of the rotary valve 62 and continuous with the channel 98. The distribution feature 92 is configured to convey the lubricant to the outer wall 94 of the rotary valve 62, where a film of lubricant is formed to facilitate a seal at an interface of the rotary valve 62 and the rear head 28 and/or valve plate assembly 30.

FIGS. 5-6 illustrate an embodiment of the valve plate assembly 30. The valve plate assembly 30 includes an outer portion 104 which interfaces with the outer wall 84 of the disc portion 70 of the rotary valve 62 and an inner portion 106 that interfaces with the second surface 76 of the disc portion 70 of the rotary valve 62. The outer portion 104 overlaps the inner portion 106. The outer portion 104 has a thickness greater than a thickness of the inner portion 106. In certain embodiments, the valve plate assembly 30 includes a valve plate 30 a disposed circumferentially about the disc portion 70 of the rotary valve 62 and a wear plate 30 b at least partially interfacing with the valve plate 30 a. The wear plate 30 b also interfaces with the second surface 76 of the disc portion 70 of the rotary valve 62. As illustrated in FIG. 5, the valve plate assembly 30 can include one or more reed valve flapping elements 30 c such as a discharge reed and a reed valve retaining member and/or discharge gaskets. The valve plate assembly 30 can also include a suction gasket, if desired.

Referring to FIG. 6, a valve plate 30 a and wear plate 30 b are illustrated. The valve plate 30 a overlays the wear plate 30 b. The valve plate 30 a is planar and includes a centrally formed aperture 108 having a diameter substantially equal to a diameter of the disc portion 70 to receive the disc portion 70 of the rotary valve 62. Discharge ports 110 are radially formed in the valve plate 30 a and spaced apart to align with each of the cylinders 14. The valve plate 30 a can be formed from a material having a coefficient of thermal expansion substantially the same as a coefficient of thermal expansion of the material forming the rotary valve 62 and/or substantially the same as a coefficient of thermal expansion of the material forming the cylinder block 12 and/or the rear head 28. The wear plate 30 b includes a centrally formed aperture 112 having a diameter substantially equal to the diameter of the stem portion 72 of the rotary valve 62 to receive the stem portion 72 of the rotary valve 62. Discharge ports 114 are radially formed in the wear plate 30 b and are spaced apart to align with the discharge ports 110 of the valve plate 30 a and the cylinders 14. The suction apertures 36 are formed in the wear plate 30 b. Each of the suction apertures 36 have a shape corresponding to a segment of one of the cylinders 14 and align therewith. The wear plate 30 b is formed from a wear resistant and flexible material to facilitate a deflection thereof. The wear plate 30 b can be coated or sprayed with a low friction or seizure resistant material such as PTFE or MoS₂ or any other low friction coating as desired.

To assemble, the valve plate assembly 30 is positioned adjacent the cylinder block 12 so that each of the suction apertures 36 align with a segment of one cylinder 14. The rotary valve 62 is coupled to the first end 23 of the drive shaft 24 so that the rotary valve 62 is at least partially received in the suction chamber 32 and partially received in the cylinder block 12. The stem portion 72 of the rotary valve is received through the centrally formed aperture of the wear plate 30 b so that the second surface 76 of the disc portion 70 of the rotary valve 62 substantially interfaces with the wear plate 30 b. The disc portion 70 is received through the centrally formed aperture of the valve plate 30 a so that the outer wall 84 of the disc portion 70 substantially interfaces with the valve plate 30 and a wall of the rear head 28 forming the suction chamber 32. In certain embodiments, the reed valve elements 30 c can also be disposed adjacent the valve plate assembly 30. The rotary valve 62, the valve plate 30 a, and the wear plate 30 b are positioned to be concentrically aligned.

In operation, the drive shaft 24 is caused to rotate by an auxiliary drive means (not shown) such as an engine of a vehicle, for example. Rotation of the drive shaft 24 causes a corresponding rotation of the rotor assembly 20. The swash plate assembly 18 is connected to the rotor assembly 20 by the hinge mechanism 26 which allows the swash plate assembly 18 to rotate with the rotor assembly 20. During rotation, the inclination angle of the swash plate assembly 18, which can be varied as known in the art, is converted into the reciprocation of the pistons 16 within the cylinders 14 by the bearing shoes 17. A suction of a refrigerant gas and a compression of the refrigerant gas are repeated due to continuance of the reciprocation of the pistons 16.

As each of the pistons 16 transition from a top dead center (TDC) position to a bottom dead center position (BDC) within the cylinders 14, a suction pressure is generated. Likewise, as each of the pistons 16 transition from the BDC to the TDC a discharge pressure is generated. The refrigerant gas is received in the suction chamber 32 from an external refrigerant circuit (not shown). The refrigerant gas is conveyed from the suction chamber 32 through the suction apertures 36 formed in the valve plate assembly 30 to each of the cylinders 14 upon a generation of the suction pressure by the pistons 16, and the refrigerant gas is subjected to compression. The compressed refrigerant gas is discharged to the discharge chamber 34 through the discharge port 38 formed in the valve plate assembly 30 upon a generation of the discharge pressure of the pistons 16. As the rotary valve 62 rotates, the compressed refrigerant gas is prevented from entering the suction chamber 34 during discharge of compressed gas thereof by closing the suction apertures 36 formed in the valve plate assembly 30 and the refrigerant gas successively enters the cylinders 14 during a suction thereof which will be described in greater detail below.

Referring to FIGS. 7A-7D, a schematic diagram of the suction opening 86 successively cooperating with the cylinders as the rotary valve 62 rotates is shown according to an embodiment of the invention. A direction of rotation R of the rotary valve 62 is indicated by an arrow. In the embodiment illustrated, seven cylinders 14 a, 14 b, 14 c, 14 d, 14 e, 14 f, 14 g are illustrated. However, the rotary valve 62 can be adapted to cooperate with any number of cylinders as desired such as fewer than seven cylinders or more than seven cylinders.

In FIG. 7A, the rotary valve 62 is positioned at a reference angle θ_(o), wherein the reference angle θ_(o) represents the rotational position of the rotary valve 62 when the suction opening 86 is approaching the cylinder 14 a. The piston 16 within the cylinder 14 a is at the TDC position. In the embodiment illustrated an angle δ of the suction opening 86 is about 148 degrees. However, it is understood the angle δ of the suction opening 86 can be any angle as desired. In this position of the rotary valve 62, the suction opening 86 is also at least partially aligned with three other cylinders 14 b, 14 c, 14 d, wherein the pistons 16 in each of the cylinders 14 b, 14 c, 14 d are in the process of a suction stroke. The suction apertures 36 to the cylinders 14 a, 14 e, 14 f, 14 g are closed by the second surface 76 of the disc portion 70 of the rotary valve 62. The pistons 16 of the cylinders 14 e, 141, 14 g are in the process of a discharge stroke.

In FIG. 7B, the rotary valve 62 is rotated from the reference angle θ₀ to an angle θ₁ which can be 25°, for example. As the rotary valve 62 rotates from the reference angle θ_(o) to the angle θ₁, the piston 14 in the cylinder 14 a begins a suction stroke. The suction opening 86 directly aligns with the cylinder 14 a and corresponding suction aperture 36 so the refrigerant gas flows directly from the suction chamber 32, through the suction aperture 36 to the cylinder 14 a. At this position of the rotary valve 62, the suction opening 86 is also aligned with the cylinders 14 b, 14 c wherein the piston 16 in the cylinders 14 b, 14 c are in the process of a suction stroke. The suction apertures 36 to the cylinders 14 d, 14 e, 14 f, 14 g are closed by the second surface 76 of disc portion 70 of the rotary valve 62. The pistons 16 of the cylinders 14 d, 14 e, 14 f, 14 g are in the process of a discharge stroke.

In FIG. 7C, the rotary valve 62 is rotated from the reference angle θ₁ to an angle θ₂ which can be 90°, for example. As the rotary valve 62 continues to rotate from the reference angle θ_(o) to the angle θ₂, the piston 14 in the cylinder 14 a is continuing to perform the suction stroke. The suction opening 86 remains aligned with the cylinder 14 a and corresponding suction aperture 36 so the refrigerant gas can continue to flow from the suction chamber 32, through the suction aperture 36 to the cylinder 14 a. At this position of the rotary valve 62, the suction opening 86 is also aligned with the cylinder 14 g, wherein the piston 16 in the cylinder 14 g has begun to perform the suction stroke, and cylinder 14 b, wherein the piston 16 in the cylinder 14 b is still in the process of performing the suction stroke. The suction apertures 36 to the cylinders 14 c, 14 d, 14 e, 14 f are closed by the second surface 76 of the disc portion 70 of the rotary valve 62. The pistons 16 of the cylinders 14 c, 14 d, 14 e, 141 are in the process of a discharge stroke.

In FIG. 7D, the rotary valve 62 is rotated from the reference angle θ₂ to an angle θ₃ which can be 180°, for example. At this rotational position of the rotary valve 62, the piston 14 in the cylinder 14 a is at the BDC position. The second surface 76 of the disc portion 70 closes the suction aperture 36 corresponding with the cylinder 14 a. At this position of the rotary valve 62, the suction opening 86 is aligned with the cylinder 14 e, 141, 14 g, wherein the piston 16 in the cylinders 14 e, 14 f, 14 g are performing the suction stroke. The suction apertures 36 to the cylinders 14 a, 14 b, 14 c, 14 d are closed by the second surface 76 of the disc portion 70 of the rotary valve 62. The pistons 16 of the cylinders 14 c, 14 d, 14 e, 14 f are in the process of the discharge stroke.

During operation, the rotary valve 62 is configured so the refrigerant gas flowing from the suction chamber 32 to the respective cylinders 14 flows in a direction substantially parallel to a direction of the pistons traveling from TDC to BDC or substantially parallel to a longitudinal direction of the cylinders 14. According to this embodiment, the rotary valve 62 facilitates the direct flow of refrigerant gas from the suction chamber to the respective cylinder during the suction stroke and closes the flow path of the refrigerant gas during the compression and discharge stroke. This militates against undesired dead volume being added to each cylinder, undesired flow losses, and facilitates sealing. The shape and material of the rotary valve 62 and balancing feature 88 militate against deflection of the rotary valve 62, which militates against leakage of the refrigerant gas into undesired locations of the compressor 10. Further militating against leakage is the lubricant being disbursed to the outer wall 84 of the disc portion 70 of the rotary valve via the distribution feature 92. The distribution feature 92 also facilitates lubrication of the rotary valve 62 with respect to the valve plate assembly 30, drive shaft 24, and rear head 28.

The direct coupling of the rotary valve 62 to the drive shaft 24 facilitates accurate opening and closing of the suction aperture 36 regardless of the speed of the rotation of the drive shaft 24. The structure of the valve plate assembly 30, particularly the wear plate 30 b being formed from a wear proof material, is caused to deflect into the rotatory suction valve 62 during compression of the refrigerant gas. This deflection improves sealing. The outer portion 104 of the wear plate 30 b which has a thickness greater than the inner portion 106 thereof militates against deflection and substantially ensures sealing. The inner portion 106 is thinner to minimize dead volume of the cylinders 14.

From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions. 

What is claimed is:
 1. A rotary valve for controlling a supply of refrigerant gas to cylinders in a variable displacement compressor, the rotary valve comprising: a disc portion; a substantially cylindrical stem portion extending axially from the disc portion, the disc portion and the stem portion configured to be coupled to a drive shaft of the compressor; and a suction opening formed in the disc portion and configured to permit direct fluid communication between a suction chamber and at least one cylinder of the compressor.
 2. The rotary valve of claim 1, wherein the suction opening has a shape adapted to axially align the suction opening with a shape of a portion of the at least one cylinder.
 3. The rotary valve of claim 1, wherein the suction opening extends arcuately in the disc portion at an angle between about 90 degrees and 180 degrees.
 4. The rotary valve of claim 1, wherein the disc portion includes a balancing feature formed thereon.
 5. The rotary valve of claim 1, further comprising an aperture centrally disposed in the stem portion and extending through the disc portion and a slot continuous with the aperture, the aperture and the slot are configured for receiving the drive shaft.
 6. The rotary valve of claim 1, further comprising a distribution feature including a channel formed on a first surface thereof for receiving a lubricant and a plurality of grooves formed on an outer wall thereof, the plurality of grooves in fluid communication with the channel.
 7. The rotary valve of claim 1, wherein at least a portion of at least one of the stem portion and the disc portion is formed from one of a ferrous material and aluminum and coated with at least one of a low friction and seizure resistant material.
 8. A rotary valve assembly for controlling a supply of refrigerant gas to cylinders in a variable displacement compressor, the rotary valve assembly comprising: a rotary valve including a disc portion, a substantially cylindrical stem portion extending axially from the disc portion, the disc portion and the stem portion configured to be coupled to a drive shaft of the compressor, and a suction opening formed in the disc portion; a valve plate assembly including a central aperture formed therein, the aperture receiving the rotary valve; and a plurality of suction apertures formed in the valve plate assembly, wherein the suction opening aligns with at least one of the suction apertures to permit direct fluid communication between a suction chamber and at least one cylinder of the compressor.
 9. The rotary valve assembly of claim 8, wherein the suction opening extends arcuately in the disc portion between about 90 degrees and 180 degrees.
 10. The rotary valve assembly of claim 8, wherein the rotary valve includes an aperture centrally disposed therein and a slot continuous with the aperture for receiving the drive shaft.
 11. The rotary valve assembly of claim 8, wherein the valve plate assembly includes an outer portion and an inner portion, the outer portion having a thickness greater than a thickness of the inner portion.
 12. The rotary valve assembly of claim 8, wherein the valve plate assembly includes a valve plate and a wear plate, the valve plate having a centrally disposed aperture for receiving the disc portion of the rotary valve and the wear plate having a centrally disposed aperture for receiving the stem portion of the rotary valve.
 13. The rotary valve assembly of claim 12, wherein the valve plate is formed from a material having a coefficient of thermal expansion substantially the same as a coefficient of thermal expansion of at least one of the rotary valve, a cylinder block of the compressor, and a rear head of the compressor defining the suction chamber.
 14. A variable displacement compressor, comprising: a cylinder block having a plurality of cylinders annularly formed therein and a centrally formed aperture, a plurality of pistons received within the cylinders; a rear head disposed adjacent one end of the cylinder block and defining a suction chamber and discharge chamber; a crank case forming a crank chamber adjacent an other end of the cylinder block; a drive shaft rotatably received in the aperture of the cylinder block and extending through the crank chamber; a swash plate assembly rotatably coupled to the drive shaft, the swash plate assembly operably coupled to the pistons to cause a reciprocating motion thereof; a rotary valve coupled to the drive shaft, the rotary valve centrally received in the suction chamber and extending through the aperture formed in the cylinder block, wherein the rotary valve has a suction opening cooperating with the cylinders to successively provide a direct fluid communication between the suction chamber and each of the cylinders.
 15. The variable displacement compressor of claim 14, wherein a direction of flow of a refrigerant gas from the suction chamber to the cylinders is parallel to a longitudinal axis of the cylinders.
 16. The variable displacement compressor of claim 14, wherein the rotary valve includes a disc portion, a substantially cylindrical stem portion integrally formed with and extending axially from the disc portion, the disc portion and the stem portion configured to be coupled to a drive shaft of the compressor, the suction opening formed in the disc portion.
 17. The variable displacement compressor of claim 14, wherein the suction opening successively aligns with each of the cylinders during a suction stroke of the each of the pistons therein.
 18. The variable displacement compressor of claim 14, further comprising a valve plate assembly disposed intermediate the cylinder block and the rotary valve, the valve plate assembly having a plurality of suction apertures formed therein, each of the suction apertures aligning with one of the cylinders.
 19. The variable displacement compressor of claim 18, wherein the valve plate assembly includes a valve plate and a wear plate, the valve plate having a centrally disposed aperture for receiving the disc portion of the rotary valve and the wear plate having a centrally disposed aperture for receiving the stem portion of the rotary valve,
 20. The variable displacement compressor of claim 14, wherein the valve plate assembly includes an outer portion and an inner portion, the outer portion having a thickness greater than a thickness of the inner portion, wherein the valve plate is formed from a material having a coefficient of thermal expansion substantially the same as a coefficient of thermal expansion of at least one of the rotary valve, the cylinder block, and the rear head defining the suction chamber. 